Police chiefs apologised today after it emerged that a man convicted of sex attacks against women was not arrested until four years after he became a suspect.

An independent investigation has been launched into police handling of the case against children's football coach Kirk Reid, 44, who has been found guilty of stalking and attacking women for more than 12 years.

Police left Reid free to attack women for four years, despite identifying him as a suspect in a notorious unsolved series of sex attacks in 2004. A litany of errors, inaction and oversights was revealed during the nine-week trial at Kingston crown court.

Following Reid's conviction, Commander Mark Simmons, of the Metropolitan police's territorial policing unit, said: "It is clear from the evidence heard in court that the standard of investigation was not what we as an organisation, or the victims, should have expected. Reid should have been arrested sooner and I, on behalf of the MPS [Metropolitan police service] and as head of Sapphire [the police sex-crimes unit], am sorry those women who were subsequently attacked by him have been caused unnecessary suffering."

Simmonds said he had voluntarily referred the case to the Independent Police Complaints Commission (IPCC) for investigation after an internal review revealed errors in the police handling of the case. The IPCC may now call for officers to be disciplined over the mistakes.

Detective Inspector Justin Davies, of the force's homicide and serious crime command, said: "To those who knew Kirk Reid, he was, on the surface, a person who displayed no propensity to commit such a string of crimes. However, as his convictions show, he is a devious sexual predator who has preyed on women for a number of years."

Reid attacked his victims as they made their way home from nights out in the Balham, Clapham and Tooting areas of south-west London. He was found guilty of 24 sex assaults and two rapes, in 2002 and 1995, although police believe he is behind at least 71 attacks on women. Investigators suspect he could be responsible for dozens more attacks that have not been reported, and have launched a helpline for potential victims.

After reporting restrictions were lifted today, it was revealed that Reid repeatedly slipped through the police net.

Officers in Wandsworth identified that a repeat sex attacker was on the loose in September 2002, and identified Reid as a suspect in February 2004.

But despite Reid crossing their radar on several more occasions he was not held until January 2008, when Scotland Yard took on the case. Its homicide and serious crime command then took just hours to identify Reid as a prime suspect.

Police believe Reid preyed on at least 20 more women during the four-year gap. The missed opportunities to bring him to justice included:

• December 2002 – A patrol spoke to Reid and submitted an intelligence report after a member of the public told them he had been following a woman in Clapham.

• January 2004 – Officers failed to act when a man dialed 999 and gave the details of Reid's car in connection with a mystery attack on a woman in the street.

• February 2004 – Reid was identified as a suspect in the ongoing sex attacks after he was stopped for tooting his horn at a woman in the street.

• April to December 2007 – Reid's red VW Golf was checked nine times by suspicious officers as it cruiseed around south-west London late at night. They ordered that his DNA be collected and as colleagues swabbed his cheek he told them: "I have nothing to worry about."

Five days later it matched profiles on file since two indecent assaults in 2001 and a rape in 2002. Simmons, who has overall responsibility for investigating serious sex attacks, said he was specifically concerned about the "length of time" between the identification of Reid as a suspect and his arrest.

Worboys, of Rotherhithe, south-east London, was found guilty earlier this month at Croydon crown court of drugging and molesting female passengers during an 18-month reign of terror.

Reid's offences took place in three clusters along the A24 corridor, close to Clapham South, Balham and Tooting Bec tube stations. He waited until his victims walked into quiet and leafy side streets before grabbing them from behind.

The keen athlete used his strength and 6ft 2in height to overpower the women and drag them to the ground. If they fought back, screamed and shouted, or if he was disturbed, he would sprint away towards the nearest main road. Some were assaulted just metres from their front doors as they were distracted by looking for their keys or as texting friends to say they were home safely.

His first victim, who was six months' pregnant, fought him off with an umbrella after he followed her into a lift at her block of flats. One woman was raped after Reid attacked on a deserted landing leading up to her Battersea flat.

It emerged during the trial that Reid's half-brother, the police constable Roger Reid, played an important role in bringing him to justice. The Met officer said Reid confessed to the crimes during a conversation they had through a glass partition in cells at a magistrates court. He said Reid was sitting in the cell with a "sheepish" and "pathetic" expression, and suddenly said: "I did it". The police officer replied, "What all of it?" Reid said: "Yeah, they found DNA, something about a scratch."

Roger Reid told two women who claimed they were raped by Reid to contact specialist officers.

Reid will be sentenced later this year after a psychiatric assessment.